#!/usr/bin/env python

#

# This is a generalized framework for converting between SCM

# repository formats.

#

# In its current form, it's hardcoded to convert incrementally between

# git and Mercurial.

#

# To use, you must first import the first git version into Mercurial,

# and establish a mapping between the git commit hash and the hash in

# Mercurial for that version. This mapping is kept in a simple text

# file with lines like so:

#

# <git hash> <mercurial hash>

#

# To convert the rest of the repo, run:

#

# convert-repo <git-dir> <hg-dir> <mapfile>

#

# This updates the mapfile on each commit copied, so it can be

# interrupted and can be run repeatedly to copy new commits.

import sys, os, zlib, sha, time

from mercurial import hg, ui, util

class convert_git:

    def __init__(self, path):

        self.path = path

    def getheads(self):

        return [file(self.path + "/HEAD").read()[:-1]]

    def catfile(self, rev, type):

        if rev == "0" * 40: raise IOError()

        fh = os.popen("GIT_DIR=%s git-cat-file %s %s 2>/dev/null" % (self.path, type, rev))

        return fh.read()

    def getfile(self, name, rev):

        return self.catfile(rev, "blob")

    def getchanges(self, version):

        fh = os.popen("GIT_DIR=%s git-diff-tree --root -m -r %s" % (self.path, version))

        changes = []

        for l in fh:

            if "\t" not in l: continue

            m, f = l[:-1].split("\t")

            m = m.split()

            h = m[3]

            p = (m[1] == "100755")

            changes.append((f, h, p))

        return changes

    def getcommit(self, version):

        c = self.catfile(version, "commit") # read the commit hash

        end = c.find("\n\n")

        message = c[end+2:]

        l = c[:end].splitlines()

        manifest = l[0].split()[1]

        parents = []

        for e in l[1:]:

            n,v = e.split(" ", 1)

            if n == "author":

                p = v.split()

                tm, tz = p[-2:]

                author = " ".join(p[:-2])

                if author[0] == "<": author = author[1:-1]

            if n == "committer":

                p = v.split()

                tm, tz = p[-2:]

                committer = " ".join(p[:-2])

                if committer[0] == "<": committer = committer[1:-1]

                message += "\ncommitter: %s\n" % v

            if n == "parent": parents.append(v)

        tzs, tzh, tzm = tz[-5:-4] + "1", tz[-4:-2], tz[-2:]

        tz = int(tzs) * (int(tzh) * 3600 + int(tzm))

        date = tm + " " + str(tz)

        return (parents, author, date, message)

    def gettags(self):

        tags = {}

        for f in os.listdir(self.path + "/refs/tags"):

            try:

                h = file(self.path + "/refs/tags/" + f).read().strip()

                c = self.catfile(h, "tag") # read the commit hash

                h = c.splitlines()[0].split()[1]

                tags[f] = h

            except:

                pass

        return tags

class convert_mercurial:

    def __init__(self, path):

        self.path = path

        u = ui.ui()

        self.repo = hg.repository(u, path)

    def getheads(self):

        h = self.repo.changelog.heads()

        return [ hg.hex(x) for x in h ]

    def putfile(self, f, e, data):

        self.repo.wfile(f, "w").write(data)

        if self.repo.dirstate.state(f) == '?':

            self.repo.dirstate.update([f], "a")

        util.set_exec(self.repo.wjoin(f), e)

    def delfile(self, f):

        try:

            os.unlink(self.repo.wjoin(f))

            #self.repo.remove([f])

        except:

            pass

    def putcommit(self, files, parents, author, dest, text):

        seen = {}

        pl = []

        for p in parents:

            if p not in seen:

                pl.append(p)

                seen[p] = 1

        parents = pl

        if len(parents) < 2: parents.append("0" * 40)

        if len(parents) < 2: parents.append("0" * 40)

        p2 = parents.pop(0)

        while parents:

            p1 = p2

            p2 = parents.pop(0)

            self.repo.rawcommit(files, text, author, dest,

                                hg.bin(p1), hg.bin(p2))

            text = "(octopus merge fixup)\n"

            p2 = hg.hex(self.repo.changelog.tip())

        return p2

    def puttags(self, tags):

        try:

            old = self.repo.wfile(".hgtags").read()

            oldlines = old.splitlines(1)

            oldlines.sort()

        except:

            oldlines = []

        k = tags.keys()

        k.sort()

        newlines = []

        for tag in k:

            newlines.append("%s %s\n" % (tags[tag], tag))

        newlines.sort()

        if newlines != oldlines:

            #print "updating tags"

            f = self.repo.wfile(".hgtags", "w")

            f.write("".join(newlines))

            f.close()

            if not oldlines: self.repo.add([".hgtags"])

            date = "%s 0" % int(time.mktime(time.gmtime()))

            self.repo.rawcommit([".hgtags"], "update tags", "convert-repo",

                                date, self.repo.changelog.tip(), hg.nullid)

            return hg.hex(self.repo.changelog.tip())

class convert:

    def __init__(self, source, dest, mapfile):

        self.source = source

        self.dest = dest

        self.mapfile = mapfile

        self.commitcache = {}

        self.map = {}

        for l in file(self.mapfile):

            sv, dv = l[:-1].split()

            self.map[sv] = dv

    def walktree(self, heads):

        visit = heads

        known = {}

        parents = {}

        while visit:

            n = visit.pop(0)

            if n in known or n in self.map: continue

            known[n] = 1

            self.commitcache[n] = self.source.getcommit(n)

            cp = self.commitcache[n][0]

            for p in cp:

                parents.setdefault(n, []).append(p)

                visit.append(p)

        return parents

    def toposort(self, parents):

        visit = parents.keys()

        seen = {}

        children = {}

        while visit:

            n = visit.pop(0)

            if n in seen: continue

            seen[n] = 1

            pc = 0

            if n in parents:

                for p in parents[n]:

                    if p not in self.map: pc += 1

                    visit.append(p)

                    children.setdefault(p, []).append(n)

            if not pc: root = n

        s = []

        removed = {}

        visit = children.keys()

        while visit:

            n = visit.pop(0)

            if n in removed: continue

            dep = 0

            if n in parents:

                for p in parents[n]:

                    if p in self.map: continue

                    if p not in removed:

                        # we're still dependent

                        visit.append(n)

                        dep = 1

                        break

            if not dep:

                # all n's parents are in the list

                removed[n] = 1

                s.append(n)

                if n in children:

                    for c in children[n]:

                        visit.insert(0, c)

        return s

    def copy(self, rev):

        p, a, d, t = self.commitcache[rev]

        files = self.source.getchanges(rev)

        for f,v,e in files:

            try:

                data = self.source.getfile(f, v)

            except IOError, inst:

                self.dest.delfile(f)

            else:

                self.dest.putfile(f, e, data)

        r = [self.map[v] for v in p]

        f = [f for f,v,e in files]

        self.map[rev] = self.dest.putcommit(f, r, a, d, t)

        file(self.mapfile, "a").write("%s %s\n" % (rev, self.map[rev]))

    def convert(self):

        heads = self.source.getheads()

        parents = self.walktree(heads)

        t = self.toposort(parents)

        t = [n for n in t if n not in self.map]

        num = len(t)

        for c in t:

            num -= 1

            desc = self.commitcache[c][3].splitlines()[0]

            #print num, desc

            self.copy(c)

        tags = self.source.gettags()

        ctags = {}

        for k in tags:

            v = tags[k]

            if v in self.map:

                ctags[k] = self.map[v]

        if ctags:

            nrev = self.dest.puttags(ctags)

            # write another hash correspondence to override the previous

            # one so we don't end up with extra tag heads

            file(self.mapfile, "a").write("%s %s\n" % (c, nrev))

gitpath, hgpath, mapfile = sys.argv[1:]

if os.path.isdir(gitpath + "/.git"):

    gitpath += "/.git"

c = convert(convert_git(gitpath), convert_mercurial(hgpath), mapfile)

c.convert()